Chemical mechanical planarization or polishing (CMP) is the primary process to achieve local and global planarity of integrated circuits (ICs) devices. The technique typically applies CMP compositions or slurries containing abrasives and other additives as an active chemistry between a rotating substrate surface and a polishing pad under an applied load. Thus, the CMP process couples a physical process such as abrasion with a chemical process such as oxidation or chelation. It is not desirable for the removal or polishing of substrate materials to be comprised of purely physical or purely chemical action, but rather the synergistic combination of both in order to achieve a fast uniform removal.
This way, the substrate material is removed until the desired planarity is achieved or a barrier sublayer or stopping film is exposed. Ultimately, a planar, defect-free surface is obtained which enables proper multilayer IC device fabrication by subsequent photolithography, patterning, etching and thin-film processing.
Shallow trench isolation (STI) is a specific CMP application which generally requires the selective removal of silicon dioxide to silicon nitride on a patterned wafer substrate. In this case, etched trenches are overfilled with a dielectric material, e.g., silicon dioxide, which is polished using the silicon nitride barrier film as the stopping film. The CMP process ends with clearing the silicon dioxide from the barrier film while minimizing the removal of exposed silicon nitride and trench silicon dioxide.
This requires CMP slurries capable of achieving a high relative ratio of silicon dioxide material removal rate MRR to silicon nitride removal rate MRR which ratio is also referred to in the art as oxide-to-nitride selectivity.
Recently, polysilicon films are also used as barrier films or as an electrode material (cf. the American patent U.S. Pat. No. 6,626,968 B2). Therefore, it has become highly desirable to have CMP slurries and methods available which allow for the global planarization of substrates containing silicon oxide dielectric and polysilicon films. This requires CMP slurries exhibiting a high oxide-to-polysilicon selectivity.
It is even more desirable to have CMP slurries and methods available which allow for the global planarization of substrates additionally containing silicon nitride films.
In this case, the oxide-to-nitride selectivity should not be too high, in order to avoid dishing, and other damages and defects in the globally planarized, heterogeneous, patterned surface containing silicon dioxide, silicon nitride and polysilicon areas. However, the silicon nitride-to-polysilicon selectivity should also be high.
Ceria-based CMP slurries have received considerable attention in STI applications because of their ability to achieve a comparatively high oxide-to-nitride selectivity due to the high chemical affinity of ceria to silicon dioxide which is also referred to in the art as the chemical tooth action of ceria.
Nevertheless, the oxide-to-polysilicon selectivity of ceria-based CMP slurries must be improved by additives which “tailor” the selectivity.
Numerous attempts have been made to tailor the selectivity of ceria-based CMP slurries.
Thus, Jae-Don Lee et al. disclose in Journal of the Electrochemical Society, 149 (8), G477-G481, 2002, the effects of nonionic surfactants with different hydrophile-lipophile-balance (HLB) values such as polyethyleneoxides, ethyleneoxide-propyleneoxide copolymers and ethyleneoxide-propyleneoxide-ethyleneoxide triblock copolymers on oxide-to-polysilicon selectivity during CMP. However, fumed silica is used as the abrasive and the oxide-to-nitride selectivity is not addressed.
The American patent application US 2002/0034875 A1 and the American patent U.S. Pat. No. 6,626,968 B2 disclose a ceria-based CMP slurry containing surfactants, pH adjusting agents such as potassium hydroxide, sulfuric acid, nitric acid, hydrochloric acid or phosphoric acid, and polymers containing a hydrophilic functional group and a lipophilic functional group such as polyvinyl methyl ether (PVME), polyethylene glycol (PEG), polyoxyethylene 23 lauryl ether (POLE), polypropanoic acid (PPA), polyacrylic acid (PM), and polyether glycol bis ether (PEGBE). The ceria-based CMP slurry increases the oxide-to-polysilicon selectivity.
The American patent U.S. Pat. No. 6,645,051 B2 discloses a ceria-based CMP slurry for polishing memory hard disk substrates containing at least one nonionic surfactant selected from the group consisting of polyoxyethylene polyoxypropylene alkyl ethers and polyoxyethylene polyoxypropylene copolymers.
The US patent application US 2003/0228762 A1 discloses a CMP slurry for polishing substrates containing a low-k dielectric film, the said CMP slurry containing                abrasive particles selected from the group consisting of alumina, silica, titania, ceria, zirconia, germania, magnesia, and co-formed products thereof; and        amphiphilic nonionic surfactants having at least one lipophilic head group and at least one hydrophilic tail group.        
According to the US 2003/0228762 A1, suitable head groups include polysiloxanes, tetra-C1-4-alkyldecynes, saturated or partially unsaturated C6-30 alkyl groups, polyoxypropylene groups, C6-12 alkyl phenyl or alkyl cyclohexyl groups, and polyethylene groups. Suitable tail groups include polyoxyethylene groups. Thus, the amphiphilic nonionic surfactant can be selected from the group consisting of polyoxyethylene alkyl ethers or esters.
The American patent application US 2006/0124594 A1 discloses a ceria-based CMP slurry having a viscosity of at least 1.5 cP and comprising a viscosity increasing agent including a nonionic polymer such as polyethylene glycol (PEG). The ceria-based CMP slurry is said to have a high oxide-to-nitride selectivity and to cause a low within-wafer non-uniformity WIWNU.
The American patent application US 2006/0216935 A1 discloses a ceria-based CMP slurry comprising protein, lysine and/or arginine and a pyrrolidone compounds such as polyvinylpyrrolidone (PVP), N-octyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-butyl-2-pyrrolidone, N-hexyl-2-pyrrolidone, N-decyl-2-pyrrolidone, N-octadecyl-2-pyrrolidone, and N-hexadecyl-2-pyrrolidone. The ceria-based CMP slurry can furthermore contain dispersing agents like polyacrylic acid, glycols and polyglycols. Specific examples use proline, polyvinylpyrrolidone or N-octyl-2-pyrrolidone, PPO/PEO blockcopolymers, and glutaraldehyde. The ceria-based CMP slurry is believed to not aggressively remove trench silicon dioxide thereby allowing for extended polishing beyond the endpoint without substantially increasing the minimum step height.
The American patent application US 2007/0077865 A1 discloses a ceria-based CMP slurry containing polyethyleneoxide/polypropyleneoxide copolymers preferably from the Pluronic™ family sold by BASF. The ceria-based CMP slurry can furthermore contain amino alcohols such as 2-dimethylamino-2-methyl-1-propanol (DMAMP), 2-amino-2-ethyl-1-propanol (AMP), 2-(2-aminoethylamino)ethanol, 2-(isopropylamino)ethanol, 2-(methylamino)ethanol, 2-(diethylamino)ethanol, 2-(2-dimethylamino)ethoxy)ethanol, 1,1′-[[3-(dimethylamino)propyl]imino]-bis-2-propanol, 2-(2-butylamino)ethanol, 2-(tert-butylamino)ethanol, 2-(diisopropylamino)ethanol, and N-(3-aminopropyl)morpholine. The ceria-based CMP slurry may furthermore contain quaternary ammonium compounds like tetramethylammonium hydroxide, film forming agents such as alkyl amines, alkanolamines, hydroxyl amines, phosphate esters, sodium lauryl sulfate, fatty acids, polyacrylates, polymethacrylates, polyvinylphosphonates, polymalates, polystyrene sulfonate, polyvinyl sulfate, benzotriazole, triazole, and benzoimidazole, and complexing agents such as acetylacetone, acetates, glycolates, lactates, gluconates, gallic acid, oxalates, phthalates, citrates, succinates, tartates, malates, ethylenediaminetetraacetic acid, ethylene glycol, pyrocatechol, pyrogallol, tannic acid, phosphonium salts and phosphonic acids. The ceria-based CMP slurry is believed to provide good selectivity of silicon dioxide and/or silicon nitride relative to polysilicon.
The American patent application US 2007/0175104 A1 discloses a ceria-based CMP slurry comprising a polysilicon polishing inhibitor which is selected from water-soluble polymers having a N-monosubstituted or N,N-di-substituted skeleton substituted by any members selected from the group consisting of acrylamide, methacrylamide and alpha-substituted derivatives thereof; polyethylene glycols; polyvinylpyrrolidones; alkoxylated linear aliphatic alcohols and ethyleneoxide adducts of acetylene-based diols. The ceria-based CMP slurry may contain additional water-soluble polymers such as polysaccharides like alginic acid, pectinic acid, carboxymethylcellulose, agar, curdlan, and pullulan; polycarboxylic acids such as polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polyimide acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly(p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, amino polyacrylamide, polyglyoxalic acid and their salts; and vinyl polymers such as polyvinyl alcohol, and polyacrolein. The ceria-based CMP slurry is said to have a high silicon dioxide over polysilicon selectivity.
The American patent applications US 2008/0085602 A1 and US 2008/0124913 A1 disclose a ceria-based CMP slurry containing 0.001 to 0.1% by weight of the nonionic surfactant selected from ethyleneoxide-propyleneoxide-ethyleneoxide triblock copolymers and polyacrylic acid as dispersing agent. The ceria-based slurry he said to have a high silicon dioxide and silicon nitride over polysilicon selectivity.
The American patent application US 2008/0281486 discloses a ceria-based CMP slurry containing nonionic surfactants having a hydrophilic-lipophilic balance (HLB) value in the range of from 12 to 17. The nonionic surfactants are selected from the group consisting of polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene isooctyl phenyl ether and mixtures thereof. In the CMP slurry is said to have a high silicon dioxide over polysilicon selectivity.
The fabrication of electrical devices, in particular, semiconductor integrated circuits (ICs); requires high precision methods which involve inter alia high selectivity CMP.
Although the prior art ceria-based CMP slurries may have a satisfactory oxide-to-polysilicon selectivity and may yield polished wafers having a good global and local planarity as exemplified by the within-wafer nonuniformity (WIWNU) and the wafer-to-wafer nonuniformity (WTWNU), the ever decreasing dimensions of the IC architectures, in particular ICs with LSI (large-scale integration) or VLSI (very-large-scale integration), necessitate the constant improvement of the ceria-based CMP slurries in order to and meet the ever increasing technical and economical demands of the manufacturers of integrated circuit devices.
However, this pressing need to constantly improve the prior art ceria-based CMP slurries does not only apply to the field of integrated circuit devices, but the polishing and planarization efficacy has also to be improved in the fields of manufacturing other electrical devices such as liquid crystal panels, organic electroluminescent panels, printed circuit boards, micro machines, DNA chips, micro plants, photovoltaic cells, and magnetic heads; as well as high precision mechanical devices and optical devices, in particular, optical glasses such as photo-masks, lenses and prisms, inorganic electro-conductive films such as indium tin oxide (ITO), optical integrated circuits, optical switching elements, optical waveguides, optical monocrystals such as the end faces of optical fibers and scintillators, solid laser monocrystals, sapphire substrates for blue laser LEDs, semiconductor monocrystals, and glass substrates for magnetic disks. The manufacturing of such electrical, mechanical and optical devices also requires high precision CMP process steps.
The Japanese patent application JP 2001-240850 A discloses a CMP slurry containing a alumina, zirconia or silicon carbide as the abrasive, an alkylene oxide-ethyleneoxide block or random copolymer as dispersing agent and sodium phosphate or sodium polyphosphate as an “anti-rust”.
The alkylene oxide-ethyleneoxide copolymer is of the general formula:Z-[{(AO)n/(EO)m}R1]p,wherein the indices in the variables have the following meaning:
p integer from 1 to 6;
n integer with an average value of 10 to 200;
m integer with an average value of 1 to 300;
E ethylene group;
A propylene or 1,2-, 2,3-, 1,3- or 1,4-butylene group;
Z residue of a p-hydric alcohol; and
R1 hydrogen atom, alkyl group having 1 to 18 carbon atoms or acyl group having 2 to 24 carbon atoms.
The CMP slurry is used for polishing silicon wafers, glass, aluminum, ceramic, synthetic silica, quartz and sapphire. Nothing is disclosed about silicon dioxide and/or silicon nitride over polysilicon selectivities.
The prior provisional American patent application U.S. Ser. No. 61/380,719 filed on Sep. 8, 2010 describes a ceria-based CMP slurry containing at least one water-soluble polymer selected from the group consisting of linear and branched alkylene oxide homopolymers and copolymers as disclosed in the Japanese patent application JP 2001-240850 A, the American patent applications US 2007/0077865 A1, US 2006/0124594 A1 and US 2008/0124913 A1, the American patent US 2006/0213780 A1 and the company brochure of BASF Corporation “Pluronic™ & Tetronic™ Block Copolymer Surfactants, 1996”. Moreover, the ceria-based CMP slurry contains at least one anionic phosphate dispersing agent. The ceria-based CMP slurry exhibits an excellent oxide-to-polysilicon selectivity and a high nitride-to-polysilicon selectivity coupled with an advantageous oxide-to-nitride selectivity.
The prior European patent application No. 10186886.7 filed on Oct. 7, 2010 describes a silica-based CMP slurry containing at least one amphiphilic nonionic surfactant selected from the group consisting of water-soluble or water dispersible surfactants having at least one lipophilic group (b1) selected from the group consisting of branched alkyl groups having 5 to 20 carbon atoms; and at least one hydrophilic group (b2) selected from the group consisting of polyoxyalkylene groups comprising oxyethylene monomer units (b21) and at least one type of substituted oxyalkylene monomer units (b22) wherein the substituents are selected from the group consisting of alkyl, cycloalkyl, or aryl, alkyl-cycloalkyl, alkyl-aryl, cycloalkyl-aryl and alkyl-cycloalkyl-aryl groups; the said polyoxyalkylene group containing the monomer units (b21) and (b22) in random, alternating, gradient and/or blocklike distribution. The CMP slurry exhibits high silicon dioxide, tantalum nitride and copper over ultra-low-k dielectric material selectivities.